The tools are caliber-specific but it seems if I get one for my smallest caliber (.243), it should also work on larger sizes (.308); granted, the centering process would be slower but you only have to do this (if at all) once for a given piece of brass...

The burrs from the flash hole interrupt the ring of fire from the primer, and as a result you get inconsistent ignition from shell case to shell case.
As far as the flash hole tools being caliber specific thats news to me.
I have a RCBS and it a universal tool and fits all my cases.

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If you have time to do it twice, then you have time to do it once right and put your name on it

I don't think it matters. I've shot enough test groups at 1000 yards to not see any difference in accuracy with the same lot of cases reloaded identically, half with deburred holes and the other half not.

Even did some tests with flash hole diameters uniformed to .082" with a #45 twist drill and also deburred and others not; same results.

For those who think it does, then by all means do it. Nobody shoots well with ammo they think's not as perfect as can be made.

----------------------

Lucas, how did you separate the inconsistant primer flash across a lot of primers that influence velocity from the burred flash holes changing the direction of that flash across a bunch of ammo?

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US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master

I agree with Bart. I once did it on all of my rifle brass but I have not touched the tool in years. At least none of my rifles can tell the difference with the brass I use and several can shoot sub-.5 MOA, at least to 100. Perhaps some real BR guns can tell the difference but mine can't.

I started deburing flash holes a few years ago and for what I do I don't think it makes a difference. My rifles are all sporters, all used for hunting and range practice/fun but no competitions. I have continued to debur though as I don't think it can hurt, it only takes a few minutes to do 50 cases, and you only do it once for the life of the case.

I've only had it make a really apparent difference once. Back about '92-'94 somewhere, I decided to try shooting 2520 in an M1A under 168 grain SMK's. With the stick powders I'd used I had always been able to tune in moderate loads to about 0.75 moa at 100 yards in that gun. But with 2520, about 1.25 moa is all it would do for me. By coincidence, I'd just got my first deburring tool around that time, so on a whim, I decided to try it. Immediately the groups shrank to about 0.75 moa. I got all excited. I figured that if it cut 40% off those groups, it would do the same for the stick powder groups. Nope. Didn't do anything for them. No amount of retuning did either. The sticks just didn't seem to care one way or the other in that gun.

Looking back twenty years later, I think there were two reasons it mattered. One is that I was using Federal 210M primers then, being blissfully unaware of the slamfire issue at the time. Second, the moderate load didn't fill the case at all well. I strongly suspect (though I have no interest in financing the experiment to prove it) that I simply needed a magnum primer both because spherical powders generally like a little extra ignition enthusiasm, and because of needing to better pressurize the empty space. By deburring the flash hole I had enabled a mild primer to perform just enough better to light the loose load of spherical powder more consistently. But with the right primer there's a good chance it would have made no difference.

I find the only real need comes from smaller cartridges... the smaller the cartridge, the bigger the percentage any variance is... I load several smaller than 22 Hornet, & have witnessed improvements uniforming flash holes between brands of brass ( had some that had almost twice the size, or 1/2 the size depending on how you look at it ) I've also had some that appeared to have the flash hole pressed in ( I'm sure it must have been drilled ) but had large burrs, that the decapping rod would actually contact the burr...

I've never seen a difference with my skill level on larger cartridges, but on the lil guys I have seen the difference

I have done it myself and if for nothing else my own personal peace of mind.

I use the Lyman tool and it is pretty much universal if I am not mistaken. You simply adjust the collar to set the depth, and go to town. Like mentioned it only take being done once, and it isn't much of an issue to do then, so I figure why not, I'm already trimming and deburring everything anyway.

I use my Lyman flash hole de-burring tool to get the tumbling media out of the flash holes. I like to run the brass back through corn cob media after sizing to remove any lingering case lube, and invariably, some of the media gets lodged in the flash holes. So the Lyman tool to the rescue, clean flash holes that also happen to be de-burred!

Bart B;
No scientific test were done per-se. But when a high level of accuracy is your goal, it becomes necessary to remove as many variables as possible. The flash hole burrs are one of the variables. When you sort your brass according to lot, weight. capacity, and flash hole size. It just one more step in achieving consistency and accuracy. We do it because we believe it makes a difference and it gives use confidence in our use of the best component possible.
My RCBS has a adjustable pilot stop just like the lyman that was mentioned.

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If you have time to do it twice, then you have time to do it once right and put your name on it

If you're "walking the tightrope to accuracy" as I call it, using non-optimal powder charges, then you may see some difference. If you know how to properly develop and prove a handload, to keep the powder charge on the Optimal Charge Weight level, then the difference that deburring flash holes could make will get "lost in the noise"...

El Chinook, again, I have never found a case with a hanging chad or a partially punched out flash hole, that does not mean I do not have the needle looking flash hole de-burring tool. I have two complete with the adap-ter-kit for different diameter necks, there are a few reloaders that uniform the diameter of the flash hole, having the flash hole all the same diameter helps when determining the first signs of high pressure, using the flash hole diameter to deterring the beginning of high pressure is not easy when the diameter is not know when developing loads, there are others mentors and or techniques that can help.

1" 3 shot groups at 100y with big game rifles is good enough for me.
.5" 5 shot groups at 100 years with varmint rifles is good enough for me.

Flash hole effects are more than 20 db down in the noise for me.

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The word 'forum" does not mean "not criticizing books."
"Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist.
Are we a nation of competing ideas, or a nation of forced conformity of thought?

Lucas, would you believe that many folks shooting the best scores in competition setting records along the way never deburr flash holes in their cases? And what they do with those cases equals what other do with their deburred flash holes.

Do you have stuff that shoots well enough to tell the difference with proper tests?

You may also believe that cases rest in the bottom of the chamber when they're fired.

__________________
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master

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